Generally, an acrylonitrile-butadiene-styrene resin (hereinafter, ABS resin) has excellent impact resistance, mechanical strength, surface gloss, and processability, so it has been used in wide range of electric/electronic products, vehicle parts, general goods, and the like. However, since the ABS resin includes chemically unstable double bonds in the rubber component which can be easily aged by ultraviolet rays, the ABS resin has inferior weather resistance and light resistance. The ABS resin has drastic discoloration and reduction of physical properties when being left outside for a long period of time, so it is not suitable for outdoor applications which are exposed to sunlight. In order to compensate the above drawbacks, post-processes such as coating or plating are applied to ABS resin molded articles, or large amount of ultraviolet stabilizer is added to the ABS resin when the ABS resin is being extruded. However, the former has complicated processes and high failure rates, and the later has insufficient long-lasting weather resistance and expensive manufacturing costs.
In order to overcome the application limits of the ABS resin, several resins having excellent weather resistance are used instead of the ABS resin and acrylate-styrene-acrylonitrile resin (hereinafter, ASA resin) is widely used among them.
The ASA resin is generally manufactured by mixing and extruding an acrylate-based graft polymer, which is obtained by graft-polymerizing a vinyl cyanide compound and an aromatic vinyl compound to an acrylate-based synthetic rubber through the emulsion polymerization, and a aromatic vinyl-vinyl cyanide copolymer, which is obtained by copolymerizing a vinyl cyanide compound and an aromatic vinyl compound. At this point, a resin having desired physical properties can be obtained by adjusting the physical properties and the content of an acrylate-based synthetic rubber, an acrylate-based graft polymer, and an aromatic vinyl-vinyl cyanide copolymer, which is a matrix polymer, and by selectively further adding a reinforcing material having a specific function. The ASA resin has excellent weather resistance, light resistance, chemical resistance, heat resistance, and the like, thereby being suitable for outdoor applications which are exposed to plenty of light such as outdoor electric/electronic parts, exterior parts of vehicle, construction materials, and the like.
Otherwise, an α-methyl styrene-based matrix SAN resin is conventionally used for enhancing heat resistance of an ASA resin, an existing weather resistant resin, since outdoor applications such as vehicles necessarily require heat resistance. A copolymer of a vinyl cyanide compound and an α-methyl styrene-based compound used for ensuring heat resistance has excellent heat resistance but generates plenty of gas. Thus, processing stability is reduced, gloss deterioration is caused, and further color of the copolymer is quite yellow, so it has inferior dyeability property.
Accordingly, present inventors have developed an ASA graft copolymer having enhanced impact resistance, weather resistance, and dyeability properties by structurally changing the core design of an ASA graft copolymer having a core-shell structure in order to overcome the above-mentioned problems.